1. Field of the Invention
This invention relates to a vacuum cleaner filter bag seal which is used to form disposable vacuum cleaner bags by folding one or two pieces of filter material so that two sheets of the material lie parallel and adjacent to one another. The two pieces of material are joined to one another along their edges by crimping so that these edges mechanically interlock. The crimped region is then folded over for greater strength. The invention also extends to a method of providing such a seal.
2. Description of the Related Art
It is known to form vacuum cleaner bags by either folding one or overlapping two suitably-shaped pieces of filtration material and then sealing their edges to form an airtight bag. These constructions generally required the edges of the filtration material to be joined together to prevent the escape of gas and dust.
The most common method of vacuum bag construction involves placing the two pieces which are to be joined together and then folding both of the pieces in the same direction at least once. This technique is clearly shown in U.S. Pat. No. 3,498,031, which recognizes that such a folded seal can then be stapled, glued or sewn to better maintain its shape. This sort of folded seal is also shown in U.S. Pat. No. 4,116,648.
The use of folded seams is also set forth in U.S. Pat. No. 3,859,064, which shows a bag construction having several folded edges. Before the blank is folded to form the vacuum cleaner bag, adhesive is placed on the portions of the blank which are part of the folded seal.
Several different ways of joining fabric regions together to form a vacuum bag are discussed in U.S. Pat. No. 4,164,400. This patent suggests that such seals can be formed by sewing the pieces together and then folding them over. Alternatively, this patent suggests cementing or heat-sealing the two layers together. Techniques such as heat-sealing, high-frequency sealing or induction sealing are also mentioned.
U.S. Pat. No. 4,374,888 describes a non-woven laminated material suitable for use as a recreational fabric (rather than a vacuum cleaner bag material). The layers of the laminate are bonded together in a pattern so that the laminate has the look and feel of a woven fabric. The patent teaches that bonding can be carried out using either a patterned nip or ultrasonic bonding.
Finally, U.S. Pat. No. 2,813,596 describes a filter bag structure made from one to ten plies of wadding. This patent describes the use of folded-over end portions, and it also explains that the plies of wadding which make up the bag are held together by lines of embossing formed on those plies. The patent also recognizes that the embossing can be supplemented or even replaced by adhesive, or even sewing.